Portable electronic devices typified by cell telephones and tablet computers have spread rapidly in recent years. Among such electronic devices, there are also a large number of electronic devices that employ folding structures for reasons such as compactness.
An example of a conventional folding structure for an electronic device is a structure that has a single-axis hinge between two casings, in which the two casings open and close by using the hinge rotating.
Furthermore, in order to improve durability, there is a conventional technology which has a structure that uses a hinge having two parallel axes. In addition, there is a conventional technology in which a plurality of gears are arranged between two casings to control the opening and closing of the casings. These technologies are disclosed in, for example, Japanese Laid-open Patent Publication No. 2006-228812 and Japanese Laid-open Patent Publication No. 2010-250463.